This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The microbial population associated with the mammalian body, termed the microbiota, can play a key role in human health. Microbial communities resident in the mammalian gut are complex and dynamic. Changes in species composition or relative species abundance in these communities can retard or enhance disease progression in the host. Despite much empirical evidence for its importance, we are only now starting to elucidate the composition of the microbiota and how specific alterations in the microbiota translate into changes in human health. Our long-term goal is to characterize the role of the gut microbiota, especially microbial biofilms, in suppressing or enhancing diseases such as cancer. The objective of this proposal is to determine the role of biofilm-forming microbiota in promoting tumor formation in a mouse model of colon cancer. The central hypothesis for this proposal is that elevated levels and/or altered species composition of microbial biofilms enhances colon cancer progression in the ApcMin mouse model. The ApcMin mouse animal model for colon cancer has an increased risk of tumor development in the gastrointestinal tract due to a mutation in the APC (adenomatous polyposis coli) tumor suppressor gene. The APC gene is also the most frequently mutated gene in sporadic colon tumors in humans. We will identify whether the biofilm species composition or level of biofilm formation is changed in the ApcMin mouse model of colon cancer. Our working hypothesis is that the amount of biofilm and the biofilm species composition is altered in the ApcMin mouse model of colon cancer. We will test this hypothesis by determining if total level of biofilm is increased in ApcMin compared to wild-type mice, characterizing total microbial diversity in our mouse model using 454 pyrosequencing, and by testing if tumor formation is suppressed or enhanced by altering colonic microbial community structure through the complete transfer of microbiota from the colon of a donor mouse (ApcMin or wild-type) to the sterilized colon of acceptor mice. We also will determine if bacterial species specific to the ApcMin or wild-type mouse colon directly alter tumor formation or inflammatory response in the mouse GI tract. Our working hypothesis is that altered colon microbiota enhances cancer progression in the ApcMin mouse model by stimulating a chronic inflammatory response in the colonic epithelium. We will test this hypothesis by determining if ApcMin-specific microbial species co-localize at sites of tumor formation using FISH and confocal laser scanning microscopy, by testing if microbial species specific to the ApcMin mouse induce an inflammatory response in mouse epithelial cells, and by identifying microbial products that alter tumor formation and/or inflammation in the mouse epithelium.